Triggered oscillator



Jan..14', 1941. P, B. KING, JR 2,228,278

' TRIGGERED oscILLAToR Filed March 1o,` 193s Ag l .l 68) Patented Jan. 14, 1941 UNITED STATES PATENT OFFICE TRIGGERED OSCILLATGR Application March 10,

7 Claims.

This invention relates to an oscillator which it is desired to start and stop periodically.

One of the objects of this invention is to devise an oscillator which will start generating alternating currents upon a simple impulse being imparted thereto.

Another object is to devise such an oscillator which if momentarily stopped will not start again until the impulse mentioned above is received.

A further object is to devise simple means for stopping such an oscillator.

An additional object is to device such a system by incorporating therein a gas-filled cathanode discharge tube.

The foregoing and other objects oi my invention will be best understood from the following description of exemplications thereof, reference being had to the accompanying drawing, wherein:

Fig. 1 is a diagram illustrating one embodiment of my novel oscillator;

Fig. 2 is a diagrammatic representation of a detail of the system shown in Fig. 1 as applied to an automatic telegraph system;

Fig. 3 is another diagram illustrating another embodiment of my invention; and

Fig. 4 is an additional diagram illustrating a further embodiment of my invention.

In the application of Wilcox P. Overbeck for 30 an improvement in Cathanode tube oscillators,

Serial No. 195,071, filed March 10, 1938, there is described and claimed an oscillating circuit using a so-called cathanode tube which is a gas-filled discharge tube of the type described and claimed 35 in the patents to Charles G. Smith, No. 1,962,158,

and James D. Le Van, No. 1,962,159. I have discovered that an oscillator of the type described in said Overbeek application can be positively started and stopped by the utilization of simple 40 switching means.

In Fig. l, which illustrates an oscillator of the general type described and claimed in said Overbeck application, there is shown a cathanode tube I. This cathanode tube is filled with an ionizable gas or vapor at sufcient pressure so that ionization oi said lling may be produced upon the passage of a discharge therethrough. The tube contains a cathode 2, preferably of the indirectlyheated thermionic type, having a heater element 3, whereby it may be heated to temperature of thermionic emission. There is also provided a perforated electrode 4 spaced from the cathode 2 a distance substantially greater than the mean free path of the molecules of the medium within the tube, so that a gaseous discharge may be Cil 1933, Serial No. 195,111

produced between the cathode 2 and the electrode 4 which results inthe formation of a large number of positive ions and electrons in the intervening space. Electrons from said intervening space pass through the openings in the electrode 4, which then acts as a virtual cathode for the space behind it. It is for this reason that the electrode 4 is termed a cathanode. spaced from the cathanode 4 by a distance of the order of magnitude of the mean free path of the molecules in the gas is the anode 6. Between the cathanode 4 and the anode 6 is interposed the control electrode 5. Due to the spacing between the anode Il and the cathanode 4, the discharge in the intervening space is under complete control by the voltage impressed upon the control electrode r5. As described in said patents to Smith and Le Van, it is desirable that the electrons emitted from the cathode 2 be confined to the space between the cathode and the cathanode so that such electrons cannot pass into the region controlled by the electrode 5, except through the openings in the cathanode.

In order to supply the tube with power, a conductor 'I connects the cathode 2 to the negative terminal of a suitable source of direct current. A conductor 8 connects the anode 6 to the upper end of an induction coil 9 having a tap III adjacent the opposite end thereof. A conductor II connects the tap I0 to the positive terminal of said source of direct current. Across the coil 9 is placed a condenser I2 which forms with said coil a tank circuit in which oscillating currents may be set up. In order to supply energy to the cathode-cathanode space during the production of oscillations in the tank circuit, as more fully described and claimed in said Overbeek application, a conductor I3 extends from the lower end of the coil 9 through the condenser I4 to the cathanode 4. The cathanode 4 is likewise connected back to the cathode 2 by means` Vof a leakage resistance I5. In order to supply the proper voltage to the control electrode 5 sothat oscillations may be produced, said control electrode 5 is connected to the conductor I3 through a condenser IS. Said control electrode is also connected back to the cathode through a leakage resistance I1. When such a system is set in operation, oscillations are produced in the tank circuit. These oscillations may be taken off by means of a coil I8 coupled to the coil 9. The oscillations so taken may be fed into a suitable output device I9.

If such a system as I have described above is connected to the source of direct current and Y 55 ping and starting oscillations.

oscillations are not initiated therein, the circuit will remain in such a condition of inactivity until a starting impulse is imparted to the system. In

order to supply this starting impulse, a conduc- 5 tor 23 connects the cathanode 4 to the switch arm 2| which is adapted to contact with the stationary switch contact 22. A current-limiting resistance 23 is connected between the contact 22 and the conductor which extends to the positive terminal of the direct current source. If the switch 2| is moved so -as to close the contact 22, the voltage of the source will be impressed between the cathode and the cathanode through the current-limiting resistance 23. This will produce a flow of current between thecathode and the cathanode which will generate positive ions and electrons in the intervening space, and thereupon the oscillating circuit will start operating to produce alternating currents iiowing in the tank circuit, and thus into the output device |9. Such a closure of the contact 22 need be only momentary,.inasmuch as when this contact is opened, the system will continue to generate oscillations until some steps are taken to stop such oscillations..

In order to stop oscillations in the system described above, there is provided a stationary contact 24 also adapted to cooperate with the switch arm 2|. A conductor 25 connects the contact 24 directly with the conductor 1 which leads to the cathode 2. When the switch arm 2| is moved. over into contact with the contact 24, the discharge space between the cathode and the cathanode is short-circuited through the conductor 2U, the switch arm 2|, the contact 24, and the conductors 25 and 1. This short circuit removes the possibility of voltages existing between the cathode and the cathanode, and thus stops the iiow of current between these elec- 40 trodes, and also eliminates the creation of ionization in said space. Therefore, when the switch 2| is moved into contact with the contact 24, all oscillations in the tank circuit are stopped, and

thus the alternating current ceases to ow in the output device IS.

From the above description we see that if the switch arm l2| is moved into contact with either the contact 22 or the contact 24, oscillations will be started or stopped in the system, and leach condition will persist until the switch arm 2| is moved deliberately into contact with the opposite contact so as to change the condition of operation. It will be seen, therefore, that I have devised Aa simple trigger arrangement for stop- Such a simple triggered system is useful in many applications, particularly in the art of telegraphy and other associated signalling arts.

Fig. 2 shows a detailof the system illustrated 60. in Fig. 1 as applied to the art of telegraphy. In Fig. 2, where the conductors or elements are identical with those in Fig. 1, the same reference numerals are applied thereto. In Fig. 2 there is shown a perforated tape 2B of the type which 65.A is used at the present time in automatic telegraph keying systems. This tape is provided with two lines of perforations 21 running along the length of the tape.` `The distance between adjacent perorations in the opposite lines is designed to :rep-

resent either adot or a dash. Thus, for example, two of, the openings in Fig. 2 are shown as being separated by a short distance 2B, which represents a dot, while two other openings are represented-as rbeing separated a longer distance A, which represents a dash. Below the two lines of perforations are two contacts 28 and 29. Above the two lines of perforations are the two spring contacts 39 and 3|. As the tape 28 is moved in the direction of the arrow at the left of Fig. 2, each contact above the tape will extend through an opening 21 and come into contact with the contact below the tape each time an opening passes the respective pair of contacts. As movement of the tape, however, continues, each pair of contacts is again opened until a succeeding perforation passes said pair of contacts.

In order to adapt such an arrangement to the system shown in Fig. 1, the two upper contacts 3U and 3| may be connected together by means of a conductor 32. The conductor 22 which extends to the cathanode 4 of Fig. l is then connected to the common conductor 32. The lower Contact 28 is connected to the conductor 5 of Fig. 1 while the lower contact 29 is connected to the resistance 23 of Fig. 1. Under these conditions, when a perforation passes the contacts 29 and 3|, the circuit through the resistance 23 will be closed and the system of Fig. 1 will start generating oscillations. Such oscillations will continue until a perforation passes the contacts 30 and 28, whereupon the shortcircuiting connection through the conductor 25 Will be completed, stopping the oscillations of the system. Therefore, as the perforated tape is passed through the system, there will appear in the output I9 a series of pulses of oscillations. The length of each pulse will be dependent upon the distance between the starting and stopping perforations in the tape 23. Since these distances correspond to dots and dashes, the desired code signal will be created in the output device i9.

Other means than those shown in Fig. 1 may be utilized to stop the oscillations. For example, the arrangement as shown in Fig. 3 may be utilized. In this gure where the elements are identical with those of Fig. 1, the identical reierence numerals are applied. In Fig. 3 the conductors 1 and are supplied with direct current through a control device 33 which is energized through a pair of conductors 34 from a suitable source of direct current. The controlling device 33 is devised so that it removes the direct current voltage from the conductors 1 and at any desired time. The device 33 may be, for example, a simple switch to disconnect the conductors 34 from the conductors 1 and Ii. Removal of this voltage will stop the oscillations of the system, and such oscillations will not be re-initiated merely upon an ordinary re-application 0f the direct current voltage. Therefore, in order to re-start the system, the conductor 2l! which extends from the cathanode 4 is connected to a stationary contact 35 which is paced from and adjacent a stationary contact 3S. The resistance 23 is connected between this stationary contact 36 and the conductor A pushbutton 31 is provided which in its closed position interconnects the contacts 35 and 36, thus completing the starting circuit to the cathanode 4. The pushbutton 31 is normally biased in its open position by means of a spring 38.

In Fig. 3 the system is set in oscillation by a momentary clo'sure of the pushbutton 31, and is stopped from oscillating by a removal of the voltage from the conductors 1 and either momentarily or for any desired longer period.

In thecircuitsdescribed in Figs. 1 and 3, the condenser |4 and the leakage resistance I5 impress a negative potential on the cathanode 4 so that in order to produce a gaseous discharge in the space between the cathode 2 and the cathanode 4, it is necessary for the oscillating circuit 'to swing the cathanode through a considerable "amplitude of voltage in order to make it positive, at which time the gaseous discharge is, produced. If it is desired to impress upon the cathanode a smaller voltage swing, such an arrangement asshown in Fig. 4 may be utilized. In Fig. 4 there is shown a cathanode tube 39 of the same type as described in connection with the cathanode tube l of Figs. 1 and 3. This tube is lled with an ionizable gas or vapor and contains a cathode `4D, a control element 4I, a cathanode 42,` a control electrode 43, and an anode 44. The

\ with Figs. 1 and 3.

-In order to supply the tube with power, a conductor 45 extends from the `cathode 40 to the negative terminal of a suitable source of direct current. A conductor 46 connects the anode 44 to the upper end of an induction coil 41, the

other end of which is connected by a lead 48 to the positive terminal of the source of direct current. Across the coil 41 is placed a condenser 41 which forms with said coil a tank circuit in which oscillating currents may be set up. In order to produce a feed-back into the control grid 43 so as to maintain the oscillations, a coupling coil 49 is coupled to the coil 41. One end of the coil 49 is connected by means of a conductor 5| to the control electrode 43, and the other end of said coil is connected by means of a conductor 50 to the lead 45, and thus to the cathode 40. In such a circuit, when a gaseous discharge is initiated between the cathode 40 and the cathanode 42, oscillations are set up in the tank circuit consisting of the coil 41 and the condenser 41.

In order to supply energy to the cathodecathanode` space for producing the gaseous discharge mentioned above, the following circuit arrangements are made. Between the two conductors 45 and 48 is connected a potentiometer 52. This potentiometer is provided with a tap 53 which is at a potential with respect to the -40 and the cathanode 42.

cathode 40 less than that at which a gaseous discharge will be produced between the cathode In the case of a mercury vapor-filled tube, this is preferably less than about ten volts. A conductor 54 connects said tap to one end of a coil 55 coupled to the coil 41. A conductor 56 connects the opposite end of said coil 55 to the conductor 51, and thus to the cathanode 42. By this arrangement a positive bias is impressed upon the cathanode 42 which, however, is insuiiicient of itself to initiate the gaseous discharge. However, due to the fact that the coil 55 is coupled to the coil 41, an alternating voltage due to the oscillating currents in the tank circuit will be induced in the coil 55, and thus superimposed upon the cathanode 42. A relatively small voltage swing in the positive direction will raise the voltage upon the cathanode 42 suciently to initiate the requisite gaseous discharge between the cathode 40 and the cathanode 42. Each positive swing of the voltage across the coil 55 will produce a pulse of gaseous discharge current in the cathodecathanode space. In order that the system may work properly, the varying voltages upon the electrodes 42 and 43 should be in phase. Thus, when the cathanode 42 becomes more positive, the control electrode 43 likewise becomes more positive, and upon `the passage. of thesgaseous `starting the oscillations.

potentiometer 52 is provided with a tap 58 which is at a higher positive potential than the tap "discharge, a pulse of current iiows to the anode 44 and thus to the tank circuit. These pulses of current maintain the oscillations in said tank circuit.

Since an ordinaryapplication of voltage to the conductorsV 45 and 48 will not initiate a gaseous discharge in the cathode-cathanode space, it is necessary to provide some positive means for For this purpose the 53. The voltage of the tap 58 is sucient to initiate the requisite gaseous discharge between the cathode and the cathanode. The tape 58 is connected through a current-limiting resistance 59 to a switch contact 69. A switch arm 6I is provided and adapted to be brought into contact with the Contact 68. The switch arm 6I is connected by means of a conductor 62 to one end of a parallel circuit consisting of an induction coil 63 and a condenser 64. The other end of said parallel circuit is connected to the conductor 51, and thus to the cathanode 42. When the switch arm 6I is brought into contact with the contact 60, the voltage of the tap 58 will be impressed upon the cathanode 42, and thus will initiate the operation of the system. The closure of the Contact 69 need lbe only momentary inasmuch as when the operation of the system starts, oscillations will continue and all of the requisite energy for the cathode-cathanode space will be supplied by means of the circuit including the coil 55.

The coil 63 and condenser 64 are provided for the purpose of preventing surges in the outputY of the system. application of a positive voltage to the cathanode 42 results in a relatively large surge of current in the cathode-cathanode space, which results in an excessive surge of current in the oscillating circuit and thus in the output of the system. In a telegraph system these surges manifest themselves in the output as key clicks. If, however, the coil 63 and condenser 64 are provided, they introduce a sufficient time lag in the circuit, applying starting Voltage to the cathanode to prevent a too sudden application of said starting voltage. Of course in many instances the coil 63 and condenser 64 may be entirely omitted.

The oscillations of the circuit as shown in Fig. 4 may be stopped in various ways. For example, the arrangement as shown in Fig. 1 may be used. In this case the system in Fig. 4 is provided with a stationary contact 65 adapted to cooperate with the switch arm 6I. The contact 65 is connected by means of a conductor 66 to the lead 45 and thus to the cathode 4U. When the switch arm 6l is moved into contact with the contact 65, the cathode-cathanode space is short-circuited, and the production of a gaseous discharge therein is prevented. In this way the operation of the system ceases. Of course other means of stopping the production of oscillations in Fig. 4 could likewise be used.

'I'he output of the circuit in Fig. 4, controlled as indicated above, may be fed through a coupling coil 61 to a suitable output device 68.

Of course it is to be understood that this invention is not limited to the particular details as described above, as many equivalents will suggest themselves to those skilled in the art, and the principles of this invention will iind aWide application to various electrical arts. It is accordingly desired that the appended claims bev In some instances the sudden given a broad interpretation commensurate with the scope of this invention.

What is claimed is:

l. An oscillating system comprising an electrical gaseous discharge device comprising an envelope containing electrodes including a cathode, a cathanode spaced from said cathode, an anode spaced from said cathanode, a control electrode for controlling a discharge between said cathode and said anode, and a gaseous medium in said envelope at a pressure at which substantial ionization of said medium may be produced, an oscillating circuit connected between the anode and other electrode and adapted to be maintained in oscillation by said discharge device, means for impressing a voltage upon said anode for supplying energy to said system, means for feeding energy from said oscillating circuit to the cathanode for producing a gaseous discharge in the cathode-cathanode space, additional means for supplying energy to said cathanode to start a gaseous discharge in said cathode-cathanode space for initiating the production of oscillations in said oscillating circuit, and means for preventing the feeding of energy from said oscillating circuit to said cathanode for stopping said oscillations while said anode is still applied.

2. An oscillating system comprising an electrical gaseous discharge device comprising an envelope containing electrodes including a cathode, a cathanode spaced from said cathode, an anode spaced from said cathanode, a control electrode for controlling a discharge between said cathode and said anode, and a gaseous medium in said envelope at a pressure at which substantial ionization of Said medium may be produced, an oscillating circuit connected between the anode and other electrode and adapted to be maintained in oscillation by said discharge device, means for impressing a voltage upon said anode for supplying energy to said system, means for feeding energy from said oscillating circuit to the cathanode for producing a gaseous discharge in the cathode-cathanode space, additional means for supplying a pulse of energy to said cathanode to start a gaseous discharge in said cathode-cathanode space for initiating the production of oscillations in said oscillating circuit, and means for preventing the feeding of energy from said oscillating ycircuit to said cathanode for stopping said oscillations, while said anode is still applied.

3. An oscillating system comprising an electrical gaseous discharge device comprising an envelope containing electrodes including a cathode, a cathanode spaced from said cathode, an an- Kode spaced from said cathanode, a control electrode for controlling a discharge between said cathanode and said anode, and a gaseous medium in said envelope at a pressure at which substantial ionization of said medium may be produced, an oscillating circuit connected between the anode and other electrode and adapted to be maintained in oscillation by said discharge device, means for impressing a voltage upon said anode for supplying energy to said system, means for feeding energy from said oscillating circuit to the cathanode for producing a gaseous discharge in the cathode-cathanode space, additional means for supplying energy to said cathanode to start a gaseous discharge in said cathode-cathanode space for initiating the production of oscillations in said Aoscillating circuit, and means for short-circuiting said cathode-cathanode space for stopping said oscillations.

4. An oscillating system comprising an electrical gaseous discharge device comprising an envelope containing electrodes including a cathode, a cathanode spaced from said cathode, an anode spaced from said cathanode, a control electrode for controlling a discharge between said cathanode and said anode, and a gaseous medium in said envelope at a pressure at which substantial ionization of said medium may be produced, an oscillating circuit connected between the anode and other electrode and adapted to be maintained in oscillation by said discharge device, means for impressing a Voltage upon said anode for supplying energy to said system, means for feeding energy from said oscillating circuit to the cathanode for producing a gaseous discharge in the'cathode-cathanode space, additional means for supplying energy to said cathanode to start a gaseous discharge in said cathode-cathanode space for initiating the production of oscillations in said oscillating circuit, and means for momentarily short-circuiting said cathode-cathanode space for stopping said oscillations.

5. A system comprising an electrical gaseous discharge device comprising an envelope containing a cathode, a cathanode spaced from said cathode, an anode spaced from said cathanode, a control electrode for controlling a discharge between said cathanode and said anode, and a gaseous medium in said envelope at a pressure at which substantial ionization of said medium may be produced, means for impressing a voltage upon said anode for supplying energy to said system, means for applying a positive bias to said cathanode of insufficient value to initiate a gaseous discharge between said cathode and cathanode, said positive bias continuing throughout the normal operation of the device, means for superimposing upon said positive bias an alternating voltage to periodically produce a gaseous discharge between said cathode and cathanode, and means for supplying a control voltage to said control electrode substantially in phase with said alternating voltage.

6. An oscillating system comprising an electrical gaseous discharge device comprising an envelope containing electrodes including a cathode, a cathanode spaced from said cathode, an anode spaced from said cathanode, a control electrode for controlling a discharge between said cathanode and said anode, and a gaseous medium in said envelope at a pressure at which substantial ionization of said medium may be produced, an oscillating circuit connected between the anode and other electrode and adapted to be maintained in oscillation by said discharge device, means for impressing a voltage upon said anode for supplying energy to said system, means for feeding energy from said oscillating circuit to the cathanode for producing a gaseous discharge in the cathode-cathanode space, a circuit for supplying energy to said cathanode to start a gaseous discharge in said cathode-cathanode space for initiating the production of oscillations in said oscillating circuit, and means interposed in said circuit having a suiicient time delay to prevent surges in the oscillating circuit upon the initial application of said supplyvof energy.

7. An oscillating system comprising an electrical gaseous discharge device comprising an envelope containing electrodes including a. cathode, a

cathanode spaced from said cathode. an anode spaced from said cathanode, a control electrode for controlling a discharge between said cathanode and said anode, and a gaseous medium in said envelope at a pressure at which substantial ionization of said medium may be produced, an oscillating circuit connected between the anode and other electrode and adaptedA to be maintained in oscilla-tion by said discharge device, means for impressing a voltage upon said anode for supplying energy to said system, means for feeding energy from said oscillating circuit to the cathanode for producing a gaseous discharge in the cathode-cathanode space, a circuit for supplying energy to said cathanode to start a gaseous discharge in said cathode-cathanode space for initiating the production of oscillations in said oscillating circuit, and an inductance and condenser connected in parallel and interposed in said circuit to prevent surges in the oscillating circuit upon the initial applicationV of said supply of energy.

PAUL B. KING, JR. 

